## Research conducted at the University of Bristol means a number of quantum computing algorithms may soon be able to execute calculations of a complexity far beyond what today’s computers allow us to do.

The breakthrough involves the use of a specially designed optical chip to perform what’s known as a “quantum walk” with two particles … and it suggests the era of quantum computing may be approaching faster than the scientific establishment had predicted.

A random walk – a mathematical concept with useful applications in computer science – is the trajectory of an object taking successive steps in a random direction, be it over a line (with only two possible directions) or over a multi-dimensional space. A quantum walk is the same concept, but translated to the world of quantum computing, a field in which randomness plays a central role. Quantum walks form an essential part of many of the algorithms that make this new kind of computation so promising, including search algorithms that will perform exponentially faster than the ones we use today.

For their experiments, the researchers designed a network of optical circuits in a silicon chip, and then managed to make two photons perform a quantum walk along the network at the same time. Other researchers had previously achieved quantum walk for a single photon, but this was the first time that a quantum walk was achieved with two photons.